The invention relates to a method and apparatus for controlling the operation of a signal decoder in a broadcasting system and further to a method and apparatus for broadcasting a signal.
In a broadcasting system several broadcasting methods may be used including broadcast by way of satellite, terrestrial broadcast by way of antennas, and broadcast by way of cables. Broadcasting of signals may involve the use of either analogue or digital technology. In particular in a broadcasting system using digital technology, a digital data stream can be used to broadcast a multiplicity of programmes from a plurality of broadcasters. A standard for the broadcast of digital signals is the MPEG II standard. According to this standard a plurality of compressed digital data signals, emanating from a multiplicity of broadcasters, is multiplexed into a single digital transport stream. The transport stream may be modulated on a carrier prior to transmission.
Reception of such a broadcast signal requires a decoder which demodulates the digital transport stream, decompresses it and converts it into analogue format for reception. The decoder will identify the particular signals emanating from corresponding broadcasters and will present these signals on separate channels of the television or radio, for example, as specified by an information table in the digital transport stream.
It is possible for a broadcaster to control the operation of decoders by, for example, transferring control data, decoder operations settings, or any other data for controlling the operation of the decoder. Since a standard method of broadcasting digital signals is used, any broadcaster could broadcast a signal for controlling the operation of the decoders without authorisation of the owner or users of the decoders. Such control information broadcasted by an unauthorized broadcaster could for example be deleterious to the operation of the decoder for reception of broadcast signals emanating from authorized broadcasters.
It is therefore an object of the invention to provide a method for controlling the operation of a signal decoder in a broadcasting system which will allow controlling the operation by authorized broadcasters only.
It is a further object of the invention to provide an apparatus for controlling the operation of a signal decoder in a broadcasting system, which can be implemented in decoders to allow control of the operation by authorized broadcasters only.
It is a further object of the invention to provide a method and apparatus for broadcasting a signal adapted to be used in the described method and apparatus in such a manner that only authorized broadcasters can broadcast such signals.